1. Field of the Invention
The present invention generally relates to field choppers and, more particularly, to preventing or minimizing the fanning out of pressed crop before their cutting by the cutting drum.
2. Description of the Related Technology
Field choppers are used in agriculture to cut or collect crop from a field (by means of a crop pick-up device), to feed the crop to a chopping device (usually a chopping drum or a slice chopper) via a feeding device to chop the crop and to eject the crop onto a transport vehicle (usually after being accelerated by means of a blower) through an ejection elbow that is adjustable in its position. In most cases, the harvested plants are used as silage for feeding animals or, in recent times, for biogas production.
For field choppers in current use, the feeding device comprises two or more lower rough-press rolls mounted rigidly on the frame of the field chopper and with which two or more upper rough-press rolls interact (see EP 0 519 209 A or U.S. Pat. No. 6,539,693). The upper rough-press rolls are mounted so that they can move in height against the force of one or more springs. This allows the upper rough-press rolls to deflect upwards when taking in crop. The spring has the task of applying a defined force against the upper rough-press rolls so that, on one hand, they can pre-compress the crop in interaction with the lower rough-press rolls when taking in the crop and, on the other hand, they make it possible to take in the crop and transport it to the chopping drum with the help of a rolling force. The actual cutting process is performed by the chopping drum, which is equipped with rotating blades that act against a stationary cutting blade.
The rear, upper rough-press roll is typically mounted on a rocker (see EP 0 519 209 A or DE 102 35 096 A) and can move upwards on a curved path against the force of the spring when crop is being taken in. The curved path is provided so as to guide the outer perimeter of the upper rough-press roll as close as possible to the outer diameter of the chopping drum. As a result of the upward movement of the upper roll and the spacing between its surface interacting with the crop and the chopping drum, a part of the rough-pressing effect is lost and the pressed crop decompresses and, particularly its upper half, fans out slightly downstream of the rough-press roll. When this occurs, if a rotating blade of the chopping drum comes into contact with these upper parts of the pressed crop, the fanned out material is partially compressed again and cut. However, it can be observed that, especially thin stalks and husks, the crop can be pulled through and past the stationary cutting blade by the rotating blade edge, resulting in this portion of the crop being cut for the first time by the next or a subsequent blade. This produces undesired overlengths in the cut crop, which can lead to problems in further use as silage, e.g., unacceptable for feeding animals.
In another known construction, as seen in EP 1 277 395 A, a field chopper is provided with a stationary, flat guide element arranged above a stationary cutting blade. The guide element divides the crop flow into two sub-streams, one flowing above the other. With this dividing of the flows, a sufficient rough-pressing effect cannot be achieved by the guide element.